1. Field of the Invention
The present invention relates to a gas turbine having an L-shaped vertical shape, in which a gas generator is arranged horizontally whereas an output turbine is arranged vertically, and, more particularly, to a cooling structure around the output shaft of the gas turbine.
2. Description of Related Art
The prior art relating to the field of the invention has not been found but is exemplified in FIG. 4 by the fundamental structure of the L-shaped vertical type gas turbine in which the gas generator and the output turbine are coupled in the shape of letter "L", as has been proposed by us. In FIG. 4, reference numeral 1 designates an output turbine which has an output shaft 3 arranged vertically in a casing 2. Numeral 4 designates a shaft coupling to the shaft of a pump or the like. Numeral 5 designates a gas generator which is composed of a compressor, a combustor, a drive turbine and so on and connected to one end of an intermediate duct outer casing 6 to generate a hot combustion gas. This intermediate duct outer casing 6 seals an intermediate duct inner casing 7 from the outside and feeds the output turbine 1 with the hot combustion gas from the gas generator 5.
The output turbine 1 is supported in its entirety by the upper end portion of the intermediate duct outer casing 6 such that the intermediate duct outer casing 6 supports the output turbine 1 fixedly on a baseplate 8. Thus, a the intermediate duct outer casing 6 seals up the inner casing 7 and supports the output turbine 1 stably against vibrations and shocks. Numeral 9 designates a nose cone which is supported on the outer casing 2 by a support member 10 to seal up the downstream side of the output turbine 1. Numeral 11 designates a bearing for the upper portion of the output shaft 3.
Numeral 13 designates a cylindrical casing surrounding the output shaft 3 to form a space 12 between itself and the output shaft 3. Numeral 14 designates a supporting portion for supporting the circumference of the cylindrical casing 13. Numeral 15 designates a bellows which is made of a flexible material for absorbing the vertical elongations in the axial direction and shielding the circumference of the output shaft 3 and the inside of the casing.
With this construction, the hot gas, as generated by the gas generator 5, passes the intermediate duct inner casing 7 and enters the output turbine 1 to rotate the output shaft 3 and drive the pump or the like coupled to the shaft coupling 4. The hot gas rotates the output turbine 1 and is then released from the upper portion.
In order to cool the surrounding of the output shaft, there has been the cooling structure of the L-shaped vertical type gas turbine, ventilation air is introduced to around the output shaft, and cooling air is guided to the nose cone through the hollow portion of the output shaft and to the outside of the nose cone thereby to cool the output shaft portion. On the other hand, FIG. 5 shows another cooling structure of the L-shaped vertical type gas turbine which has been proposed by us. In FIG. 5, the reference numerals 1 to 11 are identical to those of FIG. 4. Numeral 30 designates the ventilation air to be sucked from the side of a reduction gear below the baseplate 8. Numeral 31 designates an air passage for allowing the air to flow around the output shaft 3 and the baseplate 8. Numeral 32 designates a plurality of air inflow holes formed at the gas entrance portion in the circumference of an upper shaft portion 3a of the output shaft 3. Numeral 33 designates ventilation holes which are so formed through the support member 10 supporting the nose cone 9 on the outer casing 2 as to communicate with the outside of the outer casing 2.
With this construction, the hot gas, as generated by the gas generator 5, passes the intermediate duct inner casing 7 and enters the output turbine 1 to rotate the output shaft 3 and to drive the pump or the like coupled to the shaft coupling 4. The hot gas rotates the output turbine 1 and is discharged from the upper portion.
The nose cone 9 has a sealed inside structure and is evacuated to a negative pressure, as compared with the atmosphere, by the discharge of the exhaust gas. The ventilation air 30 is sucked from the outside via the air passage 31 to rise, as indicated by 30a, along the circumference of the output shaft 3 and is sucked from the air inflow holes 32 around the shaft 3a of the gas inlet portion of the output turbine 1 into the shaft portion 3a, as indicated by 30b. This shaft portion 3a has a hollow inside, through which the air 30b flows into the sealed space in the nose cone 9. The air 30b further flows, as indicated by 30c, through the ventilation holes 33 formed in the support member 10 to the outside of the outer casing 1, as indicated by 30d, so that it is discharged to the outside.
By adopting the cooling structure thus far described, the circumference of the output shaft 3 and the inside of the nose cone 9 can be considerably effectively cooled by the natural ventilation. In the existing L-shaped vertical type gas turbine of FIG. 4, the heat is confined in a portion C by the radiation and the gas coming from the seal portion. This portion C is so small in space that it cannot be forcibly cooled, although preferred so.
The L-shaped vertical type gas turbine thus far described has been developed by arranging the output turbine vertically on the basis of the horizontal type gas turbine of the prior art. In this horizontal type gas turbine of the prior art, the output shaft is arranged horizontally on the exit side (or on the lower temperature side) of the power turbine, although not shown. The horizontal type gas turbine is not so designed that it may be installed on a narrow place, but has a relatively large allowance for the space around the shaft. As a result, the inside is cooled by the natural ventilation with the ejector effect of the package inside so that no special cooling device is required.
The L-shaped vertical type gas turbine of the prior art thus far described has been developed on the basis of the aforementioned horizontal type gas turbine, and the space 12 around the output shaft 3 is made as small as possible so that the gas turbine plant may be made as compact as possible. Since this space 12 is in contact with the entrance side (or the higher temperature side) of the output turbine 1, on the other hand, only the natural convention is so insufficient that the heat is confined in the portion C of FIG. 4, as has been described hereinbefore. It is, therefore, preferable to provide a fan or the like for the forced cooling. At present, however, the space for the forced cooling is extremely restricted so that a device for enhancing the cooling effect with a small space has been desired. Although the natural ventilation shown in FIG. 5 can achieve a considerable cooling effect, on the other hand, the heat confinement in the portion C of FIG. 4 occurs, and a device for a more sufficient cooling effect has been desired.